[chepot]

i make driver with L297 and L298 (picture attached).

i test the board with mach3, when i enable the driver:
(measured voltage maybe a little bit inaccurate since i use cheap VOM meter)
voltage at output 1 = 12.5v
voltage at output 2 = 10.6v
voltage at output 3 = 12.9v
voltage at output 4 = 10.3v
and the motor producing noisy sound.
is it normal to have all output at high voltage?

then i start to step forward the motor, it spin (noisy sound gone).
when i stop sometimes noisy sound back again (output voltage relative the same but on different position), but sometimes motor producing less noisy and out put voltage (sometime on different position) :
voltage at output 1 = 12.5v
voltage at output 2 = 11.6v
voltage at output 3 = 1.3v
voltage at output 4 = 2.1v

I put 74hc14n on l297 input stage, direct connection from l297 output to l298 input.

where i do wrong?

[chepot]

updated picture (forgot to put diodes on schematic)

[Micro_CNC]

if its a static/hissing or buzzing noise, and you only get it when the motor is still, then its most likely the "Chopper" circuit doing whats its made to do, turning power on and off reasonably fast in order to limit the motors current. and prevent the components from heating up.mine is quite loud, bolted to the metal frame it is louder than my radio (Im using same drivers).

[chepot]

yes, the noise is gone when motor move.
but when motor stop, sometimes it got noisy sometimes it quite.

I set the driver to half step mode, the drive patern should be:
0101 - 0001 - 1001 - 1000 - 1010 - 0010 - 0110 - 0100.

i'm using 24v power supply, so the voltage on motor should be:
(0v 24v 0v 24v) - (0v 0v 0v 24v) - ....

but the voltage i got when I just enabled the driver is between 10v - 12v on all wire which is 1111 patern with noisy sound.
then after i move the motor and stop, I never see 24v on any motor wire

if i unplug the motor wire, enabled the driver, the voltage on every driver output is good (0v 24v 0v 24v)

[chepot]

I borrow my friend's scope and probe L297 sense input.
silent.jpg = when the motor stop and produce no sound.
stepping.jpg = when motor rotating.
noise1.jpg = when motor stop and make a noisy sound, the overlapped waveform always come from chanel#2 (bottom).
noise2.jpg = when motor stop and make a noisy sound, channel#1 steady wave, channel#2 flat.
noise3.jpg = when motor stop and make a noisy sound, both channel have overllaped waveform.
noise4.jpg = also when motor stop and make a noisy sound.

any idea where the problem is?

[nitroxygen]

The coils in the stepper motor has an inductance and a resistance. The inductance causes a current build up while the resistance creates a current maximum (ohms law: I=V/R).

The use of a sense resistor is a way to measure the current. A current will cause a voltage drop over the resistor that is proportionally to that current. Intern in the L297 is a comparator that compares the voltage over the sense resistor and that of a reference voltage. When you use a resistor of 1 ohm and set the reference voltage to 2V, the voltage drop over the resistor will be 2V when the current trough the coil and the resistor (because they are in series) is 2A. Than the chopper will cut off the power to the motor coil. This does not mean that the supply voltage is reached. Suppose the coil of the motor has a resistance of 5ohm, in series with the 1ohm sense resistor, makes 6ohm. When you supply 24V to the motor, finally there will run (24V/6ohm) 4A trough the coil. But you set the chopper to cut off the power at 2A so, then there will only be 2A*5ohm=10V over the motor.

You have some nice scoop pictures that clearly show the current build up. When the power is not chopped due to the current was not able to reach a value over 2A, the motor wont make much noise.

[chepot]

nitroxygen, my motor is bipolar 4 wire. I measured the resistance, it's 1.3 ohm.
my Rsense is 0.1 ohm, total=1.4 ohm. 2A*1.4=2.8V...I also try to reduce the vref but the output voltage still at 10v-12v.

the snapshots of the scope was taken after I put rc filter between Rsense and L297's sense input (the noise are softer, it sound like the sound you have in your ear after a loud sound came up near your ear..."ngiiing"
before I put the rc filter, the waveform on scope is a mess.

http://eu.st.com/stonline/products/l...re/an/1679.pdf
at first time, I stick to ST application note, not to put rc filter on sense line, but after I google for some clue for my probs, i found there are plenty of L297+298 board using rc filter on sense line. now i getting more and more confuse.

also I found on the net that voltage on motor output is PWM, here some snapshot (both are taken with 10x probe, 1v/div)